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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

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Chemical analysis applied to the examination of industrial and alimentary
products plays an important part In the purchase of raw materials, in the
control of manufacturing processes, and in the determination of the value,
impurities and adulterations of the finished products. It constitutes, in-
deed, a branch of chemistry worthy of assiduous cultivation by the technical
chemist who wishes to obtain a rational knowledge of Ms prime materials
and finished products, by the hygienic chemist desirous of detecting any
additions to or changes la food substances, by the commercial chemist
for the exact characterization and evaluation of commercial products,
and., In general, by experts and inspectors appointed to exact contractual
conditions in connexion with the purchases and supplies of the State.

The methods followed in these industrial and commercial analyses are
applications of general, analytical and physical chemistry to special cases ;
in some instances they are less rigorous than, and do not attain the precision
of, scientific methods, whereas In others the accuracy Is that of the most
exact scientific investigations. The choice of the method to be used is of
considerable importance in practice, which demands processes giving the
greatest exactitude compatible with the end in view at the lowest possible
expenditure of time and trouble.

In most cases numerous methods are given in the literature for the ex-
amination of any particular material, and doubt Is often felt as to which of
these methods it is preferable to employ, the more so since the differences
frequently He in details and are not of great import. Thus, without pre-
liminary trial, the analyst, especially in a new field, cannot always decide
easily which procedure will answer his purpose.

It may, further, be pointed out that, with certain products, the methods
of analysis at present available yield results which are not absolute but
relative only to the procedure employed. In such cases it is most important
that different workers use one and the same method—although perhaps not
a very accurate one—in order that the results obtained may exhibit the
necessary concordance. Then, too, certain States have felt the necessity
of issuing official standards to be attained in the analysis of various com-
modities of general interest, while in commercial and industrial circles the
custom is growing of fixing beforehand the analytical methods serving
as basis for the evaluation of the products to be dealt In.

All this shows how useful it is for the analyst to have at his command
a collection of such methods and standards for industrial and commercial
analyses as, having been either officially prescribed or repeatedly tested,
may be confidently adopted.

To this end the results obtained over a long period In the Chemical